Walworth County, SD radon potential

EPA places Walworth County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Walworth County in the 71st percentile nationally for radon potential — higher than 71% of the counties EPA has rated.

Walworth County by the numbers

Walworth County, South Dakota is home to about 5,270 people across 707.455 square miles. Population density there runs about 7 people per square mile. Within its own EPA zone, Walworth County is bigger by population than 14% of the counties that share it. EPA's geology-based Region 8 groups Walworth County with 290 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Where the national indoor average runs about 1.3 pCi/L, Walworth County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. That doesn't mean every Walworth County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Next steps for a home in Walworth County

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find South Dakota's state radon program

For Walworth County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Walworth County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Walworth County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.